Grant funds are requested to support a new research program project aimed at the long-term goal of understanding how cell-cell interactions influence the pathogenesis of hypoxic-ischemic brain injury. Glutamatergic neurotransmission in particular has been implicated in the pathogenesis of hypoxic-ischemia neuronal death. While attention in the area has centered historically around N-methyl-D-aspartate (NMDA) receptor-mediated contributions to hypoxic brain damage, recent evidence has indicated that alpha-amino-3-hydroxy-5-methyl-4- isoxazolepropionate/kainate (AMPA/KA) receptors may also be important mediators of injury in the hypoxic-ischemic brain. Elucidation of several mechanisms underlying this AMPA/KA receptor mediation is the specific goal of the present application. The proposed experiments enlist the efforts of 8 faculty investigators, collaborating on 4 highly interlinked experimental Projects and 5 supporting Cores. Project 1 will investigate the contribution of AMPA/KA receptors to hypoxic neuronal injury in cortical cell cultures, with special attention to the minority subset of AMPA/KA receptors which gate Ca2+-permeable channels. Project II will harness a recent discovery that certain benzothiadiazides can modify AMPA/KA receptor desensitization, using these drugs as probes to study the role of AMPA/KA receptor desensitization in limiting hypoxic neuronal injury. Project III will use fura-2 videomicroscopy to examine the hypothesis that AMPA/KA receptor overactivation contributes to hypoxic neuronal injury by disrupting neuronal intracellular Ca2+ homeostasis. Project IV will explore the relationship between hypoxic AMPA/KA receptor activation and free radical-mediated cell damage. These experimental sections are supported by an administrative core (A); an animal (in vivo ischemia) core (B); a histology core (C); a computing and image analysis core (D); and a statistics core (E). taken together, proposed experiments will combine molecular, cellular, and whole animal approaches to answer several specific relevant to understanding the pathogenesis of hypoxic- ischemic brain damage. Information gathered from these studies may aid the future development of effective clinical therapies for stroke and cardiac arrest.